Final answer:
OPTION A.Resonance on a filter boosts frequencies around the cut-off frequency, allowing the system to oscillate with greater amplitude at these frequencies, similar to how a child's swing height increases with timed pushes.
Step-by-step explanation:
The answer to the question is Resonance. Resonance on a filter provides a boost to a small band of frequencies centered around the cut-off frequency. This happens because the resonance phenomenon allows a system to oscillate with greater amplitude at certain frequencies, and in the context of radio receivers or other electronic filters, this means that a signal can be picked up more strongly if its frequency matches the resonant frequency of the filter's circuit.
Just like a child on a swing will swing higher with small, consistent pushes from a parent at the right frequency, a filter will 'respond' more to frequencies at its resonant point. Inductors within circuits, for instance, show large reactance at higher frequencies, thus are used to impede or filter them out, but at their resonant frequency, they allow a larger current to flow easily.